Heretofore, solar cells of various materials have been examined. Among them, a number of solar cells made by using silicon have been commercially available. They are roughly classified to crystalline silicon solar cells using single crystal silicon or polycrystal silicon and amorphous silicon solar cells.
In crystalline silicon solar cells, photoelectric transfer efficiency, which is the performance of converting light (sun) energy to electrical energy, is higher than that of amorphous silicon solar cells. However, since crystalline silicon solar cells need much energy and time for crystal growth, they are disadvantageous in terms of the cost because of the low productivity.
Amorphous silicon solar cells are advantageous in higher light absorption, wider selectable range of substrates and easier enlargement of the scale. However, photoelectric transfer efficiency of amorphous silicon solar cells is lower than that of crystalline silicon solar cells. Furthermore, although amorphous silicon solar cells are higher in productivity than crystalline silicon solar cells, they need an evacuation process for the manufacture similarly to crystalline silicon solar cells and still impose a load to the manufacturing process in terms of equipment.
On the other hand, there have been long researches of solar cells using organic materials to solve the above problems. However, many of them have poor photoelectric transfer coefficient as low as 1% and have not be turned into practical use.
Among them, dye-sensitized solar cells introduced on Nature 353, 737, (1991) are remarked because they have been proved enable to realize photoelectric transfer efficiency as high as 10% and are considered manufacturable economically. The general structure of dye-sensitized solar cells is shown in, for example, Japanese Patent Laid-open Publication No. JP-H01-220380.
As counter electrodes of dye-sensitized solar cells, platinum (Pt) exhibiting small oxidation-reduction overvoltage of redox pairs has been mainly used conventionally. However, there are other reports on a method of using simplex carbon (The Electrochemical Society of Japan, Papers for 2002 Spring Symposium, Imoto et al., 3I19) and a method of using electrically conductive polymers (The Electrochemical Society of Japan, Papers for 2002 Autumn Symposium, Yanagida et al., 2E30) as well.
Iodine is known as specifically adheres onto platinum (Pt) and enabling realization of quick charge transfer (Mol. Cryst. Liq. Cryst. (1985) 121, 285)
Further known is a method of preparing TiO2 paste in which titanium oxide (TiO2) particles are dispersed (“Latest Technology of Dye-sensitized Solar Cells” by Hironori Arakawa, CMC, pp. 45-47 (2001))
Furthermore, a method of preparing carbon carrying Pt is known as well (Japanese Patent Laid-open Publication No. JP-H05-174838).
As referred to above, Pt has been mainly used as the counter electrode. However, charge transfer velocity on Pt electrodes is not always satisfactory. In addition, although the foregoing documents report the use of simplex carbon or electrically conductive polymers, charge transfer velocity in these methods is still insufficient.
It is therefore an object of the invention to provide an electrode higher in electron transfer velocity than Pt, simplex carbon, electrically conductive polymers, and so on, a method of manufacturing same, a photoelectric transfer element using this electrode, a method of manufacturing same, an electronic device using the same electrode and a method of manufacturing same.